1. Field of the Invention
The present invention relates to an optical connector plug that holds front ends of optical fibers and couples the optical fibers to each other.
2. Description of the Related Art
In the related art, optical coupling between optical fibers used for optical communication is performed using an optical connector. The optical connector includes optical connector plugs that hold front ends of optical fibers and an optical connector adapter that fix the optical connector plugs to each other and performs optical coupling of the optical fibers.
As the optical connector, an SC-type optical connector (complying with IEC 61754-4) that couples the optical fibers to each other using a ferrule barrel-shaped body (with the outer diameter of 2.5 mm) for holding the optical fibers or a miniaturized MU-type optical connector (complying with IEC 61754-6) using a ferrule barrel-shaped body (with the outer diameter of 1.25 mm) for holding the optical fibers is used.
In recent years, Fiber To The Home (FTTH) that establishes a high speed communication environment using access networks formed by using optical fibers and connecting subscriber lines from a telephone office to homes is spreading. In this optical fiber communication, an infrared ray with a wavelength of 1.3 μm to 1.55 μm is used as light for communication. Therefore, light output tends to increase.
However, if the high-output communication light is emitted from the front ends of the optical fibers and a human body, particularly, a part such as eyes, is exposed to the communication light, there is a high possibility of having a bad affect on the human body. In particular, a high safety is required for the optical connector plugs for holding the front ends of the optical fibers led into households according to the spread of the FTTH to the households.
From this requirement, a structure of an optical connector plug that incorporates a shutter to shield a front end face of the optical fiber is disclosed (for example, refer to Japanese Patent Application Laid-Open (JP-A) No. 2005-292777 (page. 24)). The optical connector plug that incorporates the shutter is inserted into an optical connector adapter 110, the shutter is opened, and the front end of the optical fiber is exposed, and the optical connector plug is coupled to the optical connector adaptor 110.
According to contents that are described in a paragraph “0163” of JP-A No. 2005-292777 (page 24), an inner barrel (shutter holding member) biasing member such as a coil spring that biases the inner barrel (shutter holding member) to the front end side is provided at the rear end side of a holding hole of an outer barrel (grip member). When the optical connector plug is drawn from the optical connector adaptor by the inner barrel (shutter holding member) biasing member, by making the grip member (housing) become an extension state, the optical connector plug can be prevented from becoming a reduction state erroneously in a state in which the optical connector plug is not coupled to the optical connector adaptor, and safety can be raised.
For example, it is considered to incorporate a coil spring having the minute diameter where the winding outer diameter of a coil is about 1 mm into a limited space between the inner barrel (shutter holding member), a plug frame, and a stop ring, when the inner barrel (shutter holding member) biasing member is provided in the optical connector plug as illustrated in FIG. 23 of JP-A No. 2005-292777. However, it is difficult to obtain the desired spring force and stroke in the coil spring and the coil spring cannot sufficiently bias the inner barrel (shutter holding member).
Meanwhile, when a large coil spring to contain a stop ring is provided at the rear side of the inner barrel (shutter holding member) of the optical connector plug, the desired spring force and stroke can be easily obtained. The entire length of the optical connector plug needs to be increased to incorporate the coil spring and it is difficult to engage the optical connector plug in the same space as that of the related art.